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How do you check an ac unit?

How do you check to make sure an ac unit is working properly? Do most home inspectors out there try to do a temperature differential check? Or do you just see if itís blowing cold air in and warm air out? Iím not sure how much time I should be spending trying to see how well the unit is workingÖ

Re: How do you check an ac unit?

Originally Posted by Mike Krueger

How do you check to make sure an ac unit is working properly? Do most home inspectors out there try to do a temperature differential check? Or do you just see if it’s blowing cold air in and warm air out? I’m not sure how much time I should be spending trying to see how well the unit is working…

Thank you for your help!

Thank you to all of our Vets and service men and women out there!!!

When it is above 65 or so outside, I simply turn the A/C on and let it run. I set thermostat 10 degrees lower than what the owners have it set. This allows me to return it to what the owners had it set when I'm done. I always know to go back up 10 degrees.... I let the A/C run till I get cold or till I think it has been running long enough, usually 30 min or longer.

I no longer check the TD, unless I think I have a problem and then I keep that information for my own use. If it is blowing cool air then it is working as long as it has no other issues....

Re: How do you check an ac unit?

Originally Posted by Scott Patterson

When it is above 65 or so outside, I simply turn the A/C on and let it run. I set thermostat 10 degrees lower than what the owners have it set. This allows me to return it to what the owners had it set when I'm done. I always know to go back up 10 degrees.... I let the A/C run till I get cold or till I think it has been running long enough, usually 30 min or longer.

I no longer check the TD, unless I think I have a problem and then I keep that information for my own use. If it is blowing cool air then it is working as long as it has no other issues....

Thatís good to hear. I thought it was over kill checking the td when I already know itís working.

Thatís a great idea with the 10 degree thing. Do you have rights to that idea or can I use it too?

Re: How do you check an ac unit?

I always check basic temperature differential at a few areas so i can make an educated decision as to whether i think the unit is running optimally or requires servicing.
You will get cool air from a system that is only producing 8-10 degrees differential but that system is not running properly and should be serviced.

Re: How do you check an ac unit?

I use a cheap infrared thermometer and check the registers to see what temp air is coming out of them. If I find one that is way different from the rest of them I will note it in the report. I usually look for a minimum of 8-10 degrees temperature difference and if it is less than that I will say it needs repairing. I don't use the numbers in the report....only for my records.

Re: How do you check an ac unit?

AD,

How are you measuring at the plenums? Are you drilling into the ductwork and inserting temp probes? How close or far away from the coil and filter are you measuring? To what standards are you reporting this info? Curious...

Re: How do you check an ac unit?

I agree that 18 degrees is ideal and 8-10 is marginal but that is my cut off for repair. Some older system are not capable of 18 degrees so using 18 degrees would mean replacing lots of old systems that are still working to some degree and are performing their intended function albeit not as good as a newer system would. And that is why I agree with Scott that you don't put TD in the report. I'm sure you disagree!

Re: How do you check an ac unit?

I usually try to have the buyer with me and I take them outside to look at the compressor unit. I show and tell them about air flow around the unit, then bend down and have them feel the relative temps. of the liquid line and the gas line, and explain why there should be the difference and tell them that's a layman's way of checking whether the unit is cooling, etc.

Re: How do you check an ac unit?

Originally Posted by Tom Roon

I usually try to have the buyer with me and I take them outside to look at the compressor unit. I show and tell them about air flow around the unit, then bend down and have them feel the relative temps. of the liquid line and the gas line, and explain why there should be the difference and tell them that's a layman's way of checking whether the unit is cooling, etc.

That is good time to also talk about the normal expected life of a unit and the age of the existing unit.

Re: How do you check an ac unit?

I always run the heating system first. When people start complaining about how hot it is, I know it's working. Then I run the cooling system. When people start complaining about how cold it is, I know it's working. Now if someone calls me six months later complaining about the heating or cooling system not working, I just remind them about all the complaints at the time of the inspection.

Heat them up first, then cool them down. You don't want to leave people all hot and angry at your.

Re: How do you check an ac unit?

I just had a call from an inspection I did a a few months ago related to this. While I won't get into the specifics of taking TD's since that has been beat to death here on more than one occasion, I do take TD's with a photo of the readings for my notes. I don't put specific readings in the report, I just report problems since opinions about what a "good" TD and a "correct" measurement are kind of like azzholes, everyone has one.

In this particular situation, after the client had three different "technicians" out to repair a system that was working fine (only 3 years old) at the time of inspection and then having a claim disallowed, I was able to forward the photos of the nice shiny units and temperature readings providing documentation that the unit was working at the time of the inspection.
While there is some disagreement on this also, I never destroy my photos.
After a couple of years have passed, they become less important as far as redundant file back-ups, but I never intentionally destroy them since for me they are my field notes.

Re: How do you check an ac unit?

With the newer Puron refrigerant you will be hard pressed to get a TD that will be over 16 degrees.
TD readings are all dependent on the heat load that is being placed on the system.

My home is good example of a Puron system. We keep our home at 68 degrees in the summer. The TD on the system at my home as measured at the plenum will run between 12 & 16 degrees. I just took the TD at my home, it has a 16 degree TD right now. It is 86f and the RH is around 62% The interior temp in my home is 68.2f. Yes, I have a blanket and socks on but Momma is happy!

Re: How do you check an ac unit?

Assuming the outside temperature has been 60-65 degrees or better for the past 24 hours, and assuming that electrical power has been available to the unit for at least the past 12 hours, I take note of what the thermostat is set at, then crank the thermostat down and turn on the A/C unit so it will run continually while I'm doing the rest of my inspection. I immediately take a look at the outside unit to make sure it is working, then that again and the air handler/furnace after about 15-20 minutes later, to make sure things are not freezing up anywhere.

I finish my inspections with the basement, so as soon as I get down there I do take a T/D reading, looking for anything from 14 to 23 degrees T/D. If it's anywhere outside that range, I write it up as needing further evaluation by a HVAC guy. I do not drill holes, but I do only take temperature readings as close as I can get to the A-Coil. There are usually holes already there I can probe, or I can get the return air reading by sticking a thermometer into the filter slot. If all else fails, I usually can get a good enough reading of the supply side with a laser thermometer. I only report the T/D if it is pointing to a problem with the system.

After taking the T/D, I immediately turn the A/C off, but make sure the blower is still operating so that the A-Coil can warm up. I then cover the rest of the basement, and finish by cranking up and running the furnace for no less than 5 minutes to make sure it won't short cycle. This most often brings the house temperature back up to about where it was when I first arrived. The only thing I have to be careful of is to let everyone know what I'm doing and why. Otherwise it's usually the agent who gets chilly and screws up the thermostat on me.

Re: How do you check an ac unit?

Some systems installed in the basement may also have their return open and have the basement act as a return plenum with a louvered door leading to the basement. I have seen a few installed like this in eastern PA and they work fine as long as the basement is dry. The problem is that if you measure the temperature difference you are picking up about 4 or 5 degrees of cooling from the basement slab and walls.

Re: How do you check an ac unit?

I have gotten in the habit of checking the Delta T at all registers for cooling. Since the vast majority of air handlers and duct tubing is located in the attic here and most registers (for the upper level anyway) are in the ceiling (read Attic), the extraordinarily heated environment the components are located in demands that there be no voids to the piping insulation or leaks in the metal "box" that transitions from the round duct to the square register grill, in order for the living areas to feel the desired affect. Even IF the duct insulation is in tact it gets so hot in the attic at times that the duct air stream has a tough time NOT absorbing all kinds of heat on its journey.

Given all this, using an infrared thermometer at all registers tells me 2 things. 1) If the air stream at a given register in a given room is as cool as it needs to be for occupant comfort and 2) if there is a large temp differential at any one register compared to others, indicating a localized problem.

The Delta T at the plenum may be fine but due to air leakage or poor/lack of insulation or air leaks along the duct path, usually in the metal transition piece at the grill, the end result may be far less than desired.

For the report I simply mention that the A/C does not seem to be cooling X level/area as well as Y level/area in the home and defer it. We typically have 2 A/C units in homes so a comparison is easy.

If there is only one A/C, I simply mention that the system does not appear to be cooling adequately for occupant comfort and defer it.

Re: How do you check an ac unit?

Originally Posted by Bob Knauff

Given all this, using an infrared thermometer at all registers tells me 2 things. 1) If the air stream at a given register in a given room is as cool

An infrared thermometer will tell you nothing about the temperature of the air stream, it will only tell you the temperature of the surface you are actually measuring, which could be the back inside of the supply duct, the metal grill, a combination of the two, even some ceiling area around the grill ... all depending on the infrared thermometer you are using.

You actually want to know the temperature of the air, and you will need to measure that with a thermometer which measures air temperatures, not surface temperatures.

Re: How do you check an ac unit?

I also check the compressor coils for blockage, you usually have to get lower to do this. The most likely area of the coils to be dirty is the section facing the house, and most often not looked at. Stick your head in there and look, as you look at the data plate )

Re: How do you check an ac unit?

Re: How do you check an ac unit?

Originally Posted by Jerry Peck

An infrared thermometer will tell you nothing about the temperature of the air stream, it will only tell you the temperature of the surface you are actually measuring, which could be the back inside of the supply duct, the metal grill, a combination of the two, even some ceiling area around the grill ... all depending on the infrared thermometer you are using.

This is all correct and of course anyone using one of them must be aware of that fact. Also, the distances from thermometer to sampling spot can vary which can have an affect on the consistency of the readings. Add to that, even though the grills are metal, they may be heavily painted sometimes thereby creating an insulating layer. Also, if the grill is "closed" the air does not flow through it as fast and so the temperature of the metal will be different from that of an open register.

Knowing all that and factoring for it, I am comfortable (pun intended) with the method described earlier. All registers here are metal and if the A/C runs for a decent amount of time, the temperature of the metal at the grills becomes a very good indicator of cooling power at that opening, for my needs. I am careful to always read off of a flat portion of the grill and not let the target light point into the opening past the fins.

You actually want to know the temperature of the air, and you will need to measure that with a thermometer which measures air temperatures, not surface temperatures.

In a perfect world yes. The problem with that method is trying to reach registers in ceilings, particularly if they are vaulted not to mention getting a thermometer to stick in them. In this neck of the woods, as I have said. nearly all registers are in the ceiling. Even if they weren't, time constraints dictate a faster approach than inserting a mercury thermometer in each register and waiting for it to adjust. An infrared thermometer is the tool of choice.

Again, as I said, my goal is to try to determine if the room in question will be receiving enough cool (or warm) air to keep occupants comfortable and that all ducts are operating freely. This needs to be done in a timely fashion so as not to be on the job all day as well.

Re: How do you check an ac unit?

Hi guys,

Yes, many ways to check the A/C. I tell my clients I'm not a HVAC tech, and ALWAYS recommend servicing/evaluation by a qualified HVAC company. Here in the desert, a/c is too important to rely on any type of temperature check you do. I do use a IR, cheap digital, point and read thermometer. It lets me know if there is a good split from the input to the output.

Important: some of you may recall that I had a client that accused me of not running the a/c, said I couldn't have run it because the disconnect was OFF. Well, I did run it, recorded my temps. The client was a HVAC tech, I guess he never ever saw a working unit that dies the next day. Happens all the time out here! So, I now take digital pics of the digital readout at the registers, to prove (not bulletproof) that the unit was indeed working, or not working, at the time of inspection.

Re: How do you check an ac unit?

With the newer Puron refrigerant you will be hard pressed to get a TD that will be over 16 degrees.
TD readings are all dependent on the heat load that is being placed on the system.

My home is good example of a Puron system. We keep our home at 68 degrees in the summer. The TD on the system at my home as measured at the plenum will run between 12 & 16 degrees. I just took the TD at my home, it has a 16 degree TD right now. It is 86f and the RH is around 62% The interior temp in my home is 68.2f. Yes, I have a blanket and socks on but Momma is happy!

Under most conditions we see as inspectors which is houses that are between 75 and 85 degrees in the summer the new R410 refrigerant will give more than 16 degrees differential if properly charged. I see many new R410 systems with good ducting and clean filters delivering TD's of around 20.

Re: How do you check an ac unit?

Originally Posted by Dave Hill

Hi guys,

Yes, many ways to check the A/C. I tell my clients I'm not a HVAC tech, and ALWAYS recommend servicing/evaluation by a qualified HVAC company. Here in the desert, a/c is too important to rely on any type of temperature check you do. I do use a IR, cheap digital, point and read thermometer. It lets me know if there is a good split from the input to the output.

Important: some of you may recall that I had a client that accused me of not running the a/c, said I couldn't have run it because the disconnect was OFF. Well, I did run it, recorded my temps. The client was a HVAC tech, I guess he never ever saw a working unit that dies the next day. Happens all the time out here! So, I now take digital pics of the digital readout at the registers, to prove (not bulletproof) that the unit was indeed working, or not working, at the time of inspection.

be safe!

Agreed. I had a house in AZ, when we went there, the AC ran 24/7...and then some!

A/C Ducts Leaking and High Humidity

I have a 1,500 sq. ft. house that was built in the 1920's in Dallas, TX. We have an older model Carrier 2.5 ton unit. I have attached part of our inspection and it shows just the A/C portion. What do you suggest I do about the leaking ducts? Should I stay with metal ducts and fix them or change to flex ducts? Also, the plenum box's outter wrapping has come off. What do you suggest I do to fix this? Please let me know if you suggest any other work that is evident in the A/C inspection report attached. I appreciate your time and input.

Re: How do you check an ac unit?

hey all

i always check every register for either heat or ac temp.i turn on dishwasher and either ac unit or heat when i start, and as i inspect each room zap the register with a infrared thermo tool. no differential test. while doing this have found at least five registers not hooked up or to long a throw to help do anything. when you find this you feel like a hero.

Re: How do you check an ac unit?

I may be over doing it a bit, but I cehck for a diff of 16-20 degrees, I check all the registers for the proper diff. If I don't get it at the register, when I go out side I take the infrared thermo an get a super heat reading coming off the compressor fan - based on exterior temp, it is normally 20-40 degrees hotter that the surrounding ext temp. In other words, if it is 90 degrees outside, the super heat reading should be 110-130 degrees. When it is 90-95 degrees outside a good super heat reading is 115-125 degrees on average. I also check to see that the line outside is sweating back and the compressor line is hot to touch. I perform commercial inspections and I have an HVAC tech that goes with me on larger projects and I just follow hime, see what he is doing and take notes. We just performed a commercial inspection in Houston that had 66 individual AC units on the roof.....

How do you check to make sure an ac unit is working properly? Do most home inspectors out there try to do a temperature differential check? Or do you just see if itís blowing cold air in and warm air out? Iím not sure how much time I should be spending trying to see how well the unit is workingÖ

Re: How do you check an ac unit?

Originally Posted by Mike Krueger

How do you check to make sure an ac unit is working properly? Do most home inspectors out there try to do a temperature differential check? Or do you just see if itís blowing cold air in and warm air out? Iím not sure how much time I should be spending trying to see how well the unit is workingÖ

Thank you for your help!

Thank you to all of our Vets and service men and women out there!!!

IMO, it is time to establish energy conservation & efficiency codes that home inspectors will be required to check.

Yes, you would receive more money to do these new code inspections, however, the payoff in reduced energy use & utility bills would be worth it.

That code would begin with the home & continue to the duct system airflow & ballparked DELIVERED BTUH.

Home buyer's & owners need to know from an unbiased source what they are dealing with so they can deal with the situation they are confronted with.

Re: How do you check an ac unit?

IMO, it is time to establish energy conservation & efficiency codes that home inspectors will be required to check.

Yes, you would receive more money to do these new code inspections, however, the payoff in reduced energy use & utility bills would be worth it.

That code would begin with the home & continue to the duct system airflow & ballparked DELIVERED BTUH.

Home buyer's & owners need to know from an unbiased source what they are dealing with so they can deal with the situation they are confronted with.

And just why would you want home inspectors to perform this task?
Do you envision that HI have some mystical power to correct the problems we report? While you may know something about HVAC, you are barking up the wrong tree with this idea. There are people out there that are better equipped and trained to do this and it is far afield from the intent of a home inspection. We are generalists trying to advise the client on risks associated with purchasing a home, not to protect the planet.

Maybe we should mandate that HVAC techs are required to do duct blaster tests, infrared scanning of the building envelope, and CO measurement every time they arrive for any kind of service work. I can see it now, "Clogged condensate drain? $1000 for that madam, well I know it is expensive but you know the government mandated that I have to check the entire system anytime I come to your house..."

Re: How do you check an ac unit?

Originally Posted by Jim Luttrall

Maybe we should mandate that HVAC techs are required to do duct blaster tests, infrared scanning of the building envelope, and CO measurement every time they arrive for any kind of service work. I can see it now, "Clogged condensate drain? $1000 for that madam, well I know it is expensive but you know the government mandated that I have to check the entire system anytime I come to your house..."

They are already trying to do some of this to the HVAC industry.
In California it's called Title 24.

You can do a basic test like Darrell is describing in less than 15 minutes with two instruments.
It would give a lot more information then pointing an infrared thermometer at registers.

Re: How do you check an ac unit?

They are already trying to do some of this to the HVAC industry.
In California it's called Title 24.

You can do a basic test like Darrell is describing in less than 15 minutes with two instruments.
It would give a lot more information then pointing an infrared thermometer at registers.

Point is HI are not code inspectors, have NO relationship to the government and no enforcement powers and are also not bound by the incestuous relationships found in many governmental agencies.
Maybe SOMEBODY should be mandated to perform these code related tests, but leave ME out of it please.
There is no way for me as a HI to adequately size or test the capacity or performance while functioning within my licensing. Here in the lone star state, the HVAC guys would likely be bent out of shape with this since we are not allowed to even place a set of gauges on a system without a HVAC license.

Re: How do you check an ac unit?

Originally Posted by Jim Luttrall

Point is HI are not code inspectors, have NO relationship to the government and no enforcement powers and are also not bound by the incestuous relationships found in many governmental agencies.
Maybe SOMEBODY should be mandated to perform these code related tests, but leave ME out of it please.
There is no way for me as a HI to adequately size or test the capacity or performance while functioning within my licensing. Here in the lone star state, the HVAC guys would likely be bent out of shape with this since we are not allowed to even place a set of gauges on a system without a HVAC license.

I'm on the same page with you Jim, in total agreement.
HVAC is out of the scope of work you guys are hired for.
The testing I am referring to should be done by HVAC guys but sadly it typically is not in most cases.

Too many guys trying to be a one stop shop now that don't have a clue what they are doing.
Let specialist be specialist in their own areas of expertise.

Re: How do you check an ac unit?

Re: How do you check an ac unit?

Originally Posted by DavidR

I'm on the same page with you Jim, in total agreement.
HVAC is out of the scope of work you guys are hired for.
The testing I am referring to should be done by HVAC guys but sadly it typically is not in most cases.

Too many guys trying to be a one stop shop now that don't have a clue what they are doing.
Let specialist be specialist in their own areas of expertise.

You don't have to use manifold gauges to ballpark an A/C or heat pumps cooling BTUH performance. You don't need a refrigerant handling license.

All you need is a low cost anemometer to check airflow using simple math, & a low cost instrument to check Supply Air & Return Air wet bulb temps in tenths increments.

Then you use a simple Enthalpy Chart (that's in any good HVAC/R text book) to get the enthalpy change number BTUH= CFM X's 4.5 (@sea level) Enthalpy Change. You can get that simple information & print an enthalpy chart from my website. A very low cost simple procedure...

If HVAC contractor's technicians can't do that simple test of an A/Cs performance then they should NOT be allowed to do that work!

Whether Home Inspectors should do it on their own, without a mandate, is another question.

Were I an HI, I would do it for the benefit of the potential buyer or the existing home owner.

Please don't get the feeling that something this important toward reducing energy use is some kind of huge 'government' burden, it is NOT.

I don't believe in the philosophy of doing away with all government codes, regulations & laws, nor do I believe any of you are.

The right kind of regulations can lead our nation toward prosperity, the wrong kind or NO Regulation can lead to trillion$ of loss & widespread joblessness & poverty.

We've just experienced trillion$ of worldwide loss due to a lack of effective regulation in the finance & housing mortgage sectors.

You don't have to fix the problem, all you do is expose a problem that an HVAC Contractor would have to further analyze & fix.

Reducing our fossil fuel energy use is a national security & critical economic issue, that we should all be willing to do our part toward benefiting the public good & Common Wealth of our country & our people...

Re: How do you check an ac unit?

Please don't get the feeling that something this important toward reducing energy use is some kind of huge 'government' burden, it is NOT.

I don't believe in the philosophy of doing away with all government codes, regulations & laws, nor do I believe any of you are.

The right kind of regulations can lead our nation toward prosperity, the wrong kind or NO Regulation can lead to trillion$ of loss & widespread joblessness & poverty.

We've just experienced trillion$ of worldwide loss due to a lack of effective regulation in the finance & housing mortgage sectors.

You don't have to fix the problem, all you do is expose a problem that an HVAC Contractor would have to further analyze & fix.

Reducing our fossil fuel energy use is a national security & critical economic issue, that we should all be willing to do our part toward benefiting the public good & Common Wealth of our country & our people...

Voluntary information provide by Home Inspectors is one thing, what you proposed is something else entirely.

IMO, it is time to establish energy conservation & efficiency codes that home inspectors will be required to check.

Yes, you would receive more money to do these new code inspections, however, the payoff in reduced energy use & utility bills would be worth it.

There are energy codes IN PLACE that are MANDATED by the federal government and by fiat (sp?) of the EPA passed on to the states and local governments to enforce.

I won't even go into the politics of your assertions.

For a person who is not a home inspector to presume to talk about mandates that force a home inspector to do something that your own industry won't do is ludicrous and way over the line in my opinion.
Yeah, we all want to save the planet but clean up your own backyard before worrying about mine.

Re: How do you check an ac unit?

You don't have to use manifold gauges to ballpark an A/C or heat pumps cooling BTUH performance. You don't need a refrigerant handling license.

All you need is a low cost anemometer to check airflow using simple math, & a low cost instrument to check Supply Air & Return Air wet bulb temps in tenths increments.

Then you use a simple Enthalpy Chart (that's in any good HVAC/R text book) to get the enthalpy change number BTUH= CFM X's 4.5 (@sea level) Enthalpy Change. You can get that simple information & print an enthalpy chart from my website. A very low cost simple procedure...

If HVAC contractor's technicians can't do that simple test of an A/Cs performance then they should NOT be allowed to do that work!

Whether Home Inspectors should do it on their own, without a mandate, is another question.

Were I an HI, I would do it for the benefit of the potential buyer or the existing home owner.

Please don't get the feeling that something this important toward reducing energy use is some kind of huge 'government' burden, it is NOT.

I don't believe in the philosophy of doing away with all government codes, regulations & laws, nor do I believe any of you are.

The right kind of regulations can lead our nation toward prosperity, the wrong kind or NO Regulation can lead to trillion$ of loss & widespread joblessness & poverty.

We've just experienced trillion$ of worldwide loss due to a lack of effective regulation in the finance & housing mortgage sectors.

You don't have to fix the problem, all you do is expose a problem that an HVAC Contractor would have to further analyze & fix.

Reducing our fossil fuel energy use is a national security & critical economic issue, that we should all be willing to do our part toward benefiting the public good & Common Wealth of our country & our people...

First, I'm in California. Second, we are governed by Title 24 requirements in this state. Third, I can still provide the information my Client needs to proceed by simple observations and basic (all within the B&P code and SOP's prescribed by several responsible Associations.) equipment without the additional testing and equipment you are suggesting. If I wanted to add a hat as a certified energy professional I could do that freely and provide an added value to my inspections. Nothing to prohibit this.

But it is simply not required to provide the information needed for my Client to make a more informed decision. What you suggest should not be done here, is not needed for the average Home Buyer, and should not be required of a Professional Property Inspector (generalist). On any given inspection I may recommend that these other Professionals be consulted, but it is solely the decision of the Buyer or Seller. It is not the Governments place, although it is becoming so (sadly).

Re: How do you check an ac unit?

Voluntary information provide by Home Inspectors is one thing, what you proposed is something else entirely.

There are energy codes IN PLACE that are MANDATED by the federal government and by fiat (sp?) of the EPA passed on to the states and local governments to enforce.

I won't even go into the politics of your assertions.

For a person who is not a home inspector to presume to talk about mandates that force a home inspector to do something that your own industry won't do is ludicrous and way over the line in my opinion.
Yeah, we all want to save the planet but clean up your own backyard before worrying about mine.

I am NOT against HI'ers & understand your position, I will amend the other post by saying, at this point I would not mandate the BTUH test.

Without help from the media & government we will never get HVAC contractors to do what needs to be done. If Goldstar standards are passed that may help motivate HVAC Contractors to up their standards.

That does not free HIer's from doing what is right & adding it to their charges explaining to the customer its dollar savings importance.

I believe there are situations where a home inspection is required, - in any of those cases the code checks on heat & air should be required the same as an electrical code violation check is part of an inspection. If, from a safety standpoint, inspections are not thorough enough they can become worthless.

Heat & air conditioning systems have become high dollar necessities that ought to be inspected, using simple methods, as to whether they are functioning properly, - so that HIer's or your customer can refer the findings to an HVAC Contractor.

Yes, you'll always be able to find fault with any ideas that I put forth, that is easy to do. Make your inspections of much more value to your customers, your extra value ADs should get you a lot more inspections. (I know, some of U have too many now...)

However, there are economic advantages to being ready & willing to do what ought to be done - on a worldwide basis for the benefit of everyone.

Last edited by Darrell Udelhoven; 08-16-2010 at 09:21 AM.
Reason: IF Goldstar IS PASSED...

Re: How do you check an ac unit?

Originally Posted by Scott Patterson

With the newer Puron refrigerant you will be hard pressed to get a TD that will be over 16 degrees.

I don't know about the installations in your area, but here in Florida I have yet to find one of the units with R-410a that is less than 20 degrees. In fact, most are 22 to 26 degrees. I just had a new unit installed at my home last week and I am running 24 to 25 degrees.

The temp needs to be checked with a good thermometer as close to the the coil (both in and out) to get any meaningful numbers. Checking at the return grill is OK if it right below the unit. If it is a remote return, the numbers are not going to be that accurate. likewise checking at a discharge grill 20 feet from the unit will not give good results.

Re: How do you check an ac unit?

Originally Posted by Robert Sole

I don't know about the installations in your area, but here in Florida I have yet to find one of the units with R-410a that is less than 20 degrees. In fact, most are 22 to 26 degrees. I just had a new unit installed at my home last week and I am running 24 to 25 degrees.

The temp needs to be checked with a good thermometer as close to the the coil (both in and out) to get any meaningful numbers. Checking at the return grill is OK if it right below the unit. If it is a remote return, the numbers are not going to be that accurate. likewise checking at a discharge grill 20 feet from the unit will not give good results.

Whether the TD is high, or low, or in between, the TD ... TELLS YOU NOTHING ... about the air conditioning SYSTEM, and NOTHING about the units themselves either. Well, okay, maybe "NOTHING" is a bit strong, but "VERY LITTLE" and "NOTHING WORTH RELYING ON" are definitely accurate.

If the TD is "high" (whatever "high" is) you may have an air flow problem, fan speed too low, duct restriction, etc.

There is just no USEFUL INFORMATION a home inspector will get by taking a TD.

Re: How do you check an ac unit?

Originally Posted by Jerry Peck

Whether the TD is high, or low, or in between, the TD ... TELLS YOU NOTHING ... about the air conditioning SYSTEM, and NOTHING about the units themselves either. Well, okay, maybe "NOTHING" is a bit strong, but "VERY LITTLE" and "NOTHING WORTH RELYING ON" are definitely accurate.

If the TD is "high" (whatever "high" is) you may have an air flow problem, fan speed too low, duct restriction, etc.

There is just no USEFUL INFORMATION a home inspector will get by taking a TD.

Re: How do you check an ac unit?

Originally Posted by Jerry Peck

There is just no USEFUL INFORMATION a home inspector will get by taking a TD.

I have to respectfully disagree. While the differential temperature does not tell you everything, it does provide "useful information". If the system has been running long enough to stabilize, it does give you a clue as to whether the system is going to cool the home properly or not.

If I get a differential temperature of 10 to 14 degrees, I know that the unit is not going to keep a home comfortable here in Florida when the outside temperature is in the 90's and the humidity is 70 or 80 %. At least not economically. Likewise, if the differential temperature is in the 30's , the unit is either freezing up or is very close to doing so.

You are correct that relying just on the differential temperature is not the same as using pressure gauges to check the system pressures and an amp meter to check current draw, etc. These, however, are checks that are beyond what a home inspector should be doing (even if he is properly trained IMO).

Just as with many things we do during a home inspection, we are looking for something to give us a little more information about whether things are working at the time of the inspection.

You are also correct that if you are taking these temperatures with an IR thermometer (or other thermometer for that matter) far away from the coil, the numbers are not useful. At that point it just says that the air is cooler than it was.

You are also correct in that the numbers will be skewed if there are other problems such as restricted air flow etc. But isn't that what we are trying to find out? If we have something more than just saying that the system doesn't seem to be cooling the house to use to explain to the buyer that they should have a qualified contractor service or test the system, isn't that helpful?

An air conditioner that is under-performing may in fact cool the home but it is going to cost the homeowner a lot in their electric bill. ( I know personally. My unit had a small leak and the differential temperature got down to 16 degrees. I had a $500 electric bill until I could get some freon for it. On the other hand, if the temperature stayed around 20 degrees, my bill was a lot lower).

I have a comment in my report saying that if the customer can not verify that the unit was serviced in the past year that they should consider having it serviced. The problem is that most are not going to do that unless you provide some information that reinforces that recommendation.

Re: How do you check an ac unit?

Originally Posted by Robert Sole

I have to respectfully disagree. While the differential temperature does not tell you everything, it does provide "useful information". If the system has been running long enough to stabilize, it does give you a clue as to whether the system is going to cool the home properly or not.

That is where you are wrong.

All that will tell you is if the system is going to cool the home ... or not. (leave out "properly" as it does not tell you anything about how "properly" the system is going to cool anything).

You can always indicate to the customer, that they might refer your data findings to an HVAC Contractor for further investigation.

I agree with you Darrell, there is a lot more you can do to be more accurate. RH is a big part of the reason I said that the system had to run long enough to stabilize. If it is performing correctly, it will have lowered the RH to a reasonable level and the temperature will tell you something. By no means to I mean to indicate that it tells you everything. It is a part of what you need to look at.

I think one of the main reasons that home inspectors go wrong with taking differential temperatures (and why many A/C techs cringe when they hear it) is that they turn on the unit and start taking the reading. In a high humidity area like Florida, you are not going to get meaningful information. Perhaps this is what the rude but esteemed Mr Peck was trying to indicate. (Notice that my reply to Mr. Peck was polite unlike his response to me).

Once the system has stabilized the temperatures do give you an idea of how well the system is going to work. It is more accurate than just holding your hand on the return line as I have heard suggested.

Re: How do you check an ac unit?

Originally Posted by Robert Sole

Perhaps this is what the rude but esteemed Mr Peck was trying to indicate. (Notice that my reply to Mr. Peck was polite unlike his response to me).

If you think that was a rude comment, you have a VERY THIN SKIN, that comment was simply and straight forward factual, no puddy footin' around the mulberry bush - just Plain Jane factual. Maybe you prefer sugar coating responses?

Re: How do you check an ac unit?

Originally Posted by Jerry Peck

If you think that was a rude comment, you have a VERY THIN SKIN, that comment was simply and straight forward factual, no puddy footin' around the mulberry bush - just Plain Jane factual. Maybe you prefer sugar coating responses?

We need to take it a little more gentlemanly.

Factually speaking, I've been an HVAC Tech since the mid-1970's, & what I stated comports to reality.

Unless you can prove your generalist claims to be the reality, I wouldn't be calling someone else wrong.

Re: How do you check an ac unit?

You don't have to use manifold gauges to ballpark an A/C or heat pumps cooling BTUH performance. You don't need a refrigerant handling license.

All you need is a low cost anemometer to check airflow using simple math, & a low cost instrument to check Supply Air & Return Air wet bulb temps in tenths increments.

Then you use a simple Enthalpy Chart (that's in any good HVAC/R text book) to get the enthalpy change number BTUH= CFM X's 4.5 (@sea level) Enthalpy Change. You can get that simple information & print an enthalpy chart from my website. A very low cost simple procedure...

If HVAC contractor's technicians can't do that simple test of an A/Cs performance then they should NOT be allowed to do that work!

Sadly enough Darrell probably 90% of HVAC contractors don't have a clue on how to measured delivered BTUs.

Teaching contractors to use fan charts and interpret fan data is a bit easier than teaching someone to use a low cost vane anemometer which will give suspect readings to begin with for measuring air volume.

Most contractors who try to do a good job have been fed the line that high SEER equipment and tight duct systems designed according to Manual D fix everything.
Until contractors stop believing this things won't change regardless of how involved the government and code regulations are.
Both of the latter tend to screw things up more than correct them.

Re: How do you check an ac unit?

Originally Posted by DavidR

Sadly enough Darrell probably 90% of HVAC contractors don't have a clue on how to measured delivered BTUs.

Teaching contractors to use fan charts and interpret fan data is a bit easier than teaching someone to use a low cost vane anemometer which will give suspect readings to begin with for measuring air volume.

Most contractors who try to do a good job have been fed the line that high SEER equipment and tight duct systems designed according to Manual D fix everything.
Until contractors stop believing this things won't change regardless of how involved the government and code regulations are.
Both of the latter tend to screw things up more than correct them.

Yes it is a sad situation to witness.

Folks will pay big money for very high SEER not realizing that that rating will depend on many factors that affect performance that are not performed properly or are simply ignored.

They have no idea how inefficient their brand new 20-SEER unit, may actually be, due to an improper install & horrible duct system & airflow, etc.

The home, duct & airflow system should be key elements of a future whole house energy conservation contracting era, but will that ever really happen?

That is where real savings have an opportunity to be made to happen, the high SEER (IMHO) will only work properly when placed within that equation...

The HVAC consumer tends to believe whatever contractor they have been using, & up to this point in time, most will ignore what really counts toward reducing home energy usage, - because it might initially cost a little more...

Re: How do you check an ac unit?

Factually speaking, I've been an HVAC Tech since the mid-1970's, & what I stated comports to reality.

Unless you can prove your generalist claims to be the reality, I wouldn't be calling someone else wrong.

Let us all be civilized as possible on these forums.

I have to agree with you again Darrell. There is no reason for acting as though you have the only right answers. There are going to be differences of opinion, and that is good. It helps sort through things. Many times the debates will help someone else find that at least a part of each side is good. Personally, I refuse to get into the name calling or telling someone that they are wrong. If I disagree, I will explain my side of it and let them know why I feel that my opinion is correct. We all need to act professionally. Other wise, our opinion is regarded with much less respect.

The debate on taking differential temperatures has been going on for many years. Some people are adamantly opposed and feel that there is "NO USEFUL INFORMATION" to be gained by taking them. Others, like myself, feel that while they do not tell you everything, that it is a useful part of evaluating an A/C system.

One thing is a fact. Every A/C tech I have seen checking an A/C system in the past 25 years that I have been involved with construction does check the differential temperature of the unit he is working on. That tells me that there is a benefit to doing so.

Re: How do you check an ac unit?

Originally Posted by Mike Krueger

How do you check to make sure an ac unit is working properly? Do most home inspectors out there try to do a temperature differential check? Or do you just see if itís blowing cold air in and warm air out? Iím not sure how much time I should be spending trying to see how well the unit is workingÖ

Thank you for your help!

Thank you to all of our Vets and service men and women out there!!!

I have just goten into the habit of checking the TD as I just want to know the system is opperating in normal range.

Re: How do you check an ac unit?

Be careful useing TD as a guide in very high seer systems. These systems can have the ability to stage, change speed of both the air handler blower and the condenser fan. You could come across a 5 ton system delivering only 1000 cfm. I still don't believe it is an HI's job to make a definitive call on whether a system if operating correctly. He should note that the system seems to be working correctly, or not, and should be checked by a contractor. If you plan on testing the system to determine it's efficiency, Make sure you get paid for it. And be ready to back it up.

Re: How do you check an ac unit?

My attempt at replying to Mike K's question:

1. Set the thermostat so the unit will run for a couple of hours. Note the current temperature in the location of the thermostat.
2. Inspect the kitchen to give the entire system time to stabilize.
3. Use an IR thermometer (point & shoot) and the palm of your hand to check that cool air is coming from each register in the house. This can be done as your inspection routine progresses through each room.
4. Near the end of the home inspection, walk through the house again to see if there are any obvious condensation issues, warmer rooms, etc.
5. Near the end of the two hours, not the current temperature in the location of the thermostat looking for a reduction you feel is appropriate for a functioning system.
6. Perform the exterior and attic inspections including the visual inspections of the AC components and ducts.
7. Report your observations and recommendations.

Re: How do you check an ac unit?

Originally Posted by Bailey John

Often times there is a clean out opening in the line located near the unit. The line becomes cloged with mold and fungus, Pour a cup of bleach down the line. Wait about 30 minuites then pour a pitcher of water down the line. Have somebody outside watching to see all the stuff that comes out.

Re: How do you check an ac unit?

I just purchased a Lennox XC17 air conditioning unit (and heating unit also). Anyway, the air conditioning doesn't even cool my upstairs as well as my old unit. The unit is twice the size, and they made some mighty big guarantees on satisfaction. They came once and adjusted the guages and spoke of 100's of different setting changes to make this right. Whatever he did was meaningless and changed nothing. Next they came and added a return air vent in the basement out in the hallway from the unit. This really made no impact either. There could be a slight change but nothing notable. I paid 12,000+ for this unit. I've made it clear that I am not really interested in energy saving...my energy bills are quite nice. I wanted a unit like they described...that would cool evenly and continually, and circulate the air continually. Shouldn't it be cooling my upstairs as well?? What could be the problem?

Re: How do you check an ac unit?

I always find temp readings are never the same room to room. Some bathrooms have a lot of air and a back bedroom is getting very little air.

Its been a standard statement in my reports to have an HVAC check each room and adjust the air flow as this is something that never gets check or a proper adjustment.

Best

Ron

I have seen a lot of new HVAC installs where air flow dampers were not installed at the register. In the past I have seen sliders in the register, nowadays it appears to be cheaper to provide the register boxes without them and hope the restriction in the supply ducting will provide load balancing.

Re: How do you check an ac unit?

Not sure if I'm doing this correctly but I had to chime in. Twenty yrs in home inspection & five yrs as a AC t&B tech. Anyone who is not doing a full inspection of the AC, or doesn't know how, should not even try. TD's were set in place for a reason. But there's many other factor of a proper working systems. We are professionals and should know how to fully inspect a component, learn how, or stop inspecting. Just the other day I found a temp split to be 13 degrees. Called in a tech and found the unit be a couple pounds low. This was a brand new unit. This is just Scratching the surface of proper inspection. So many other factors should be inspected as well. "Delta P, coil condition, proper size ext...

Re: How do you check an ac unit?

Originally Posted by Vivian Deaton

I just purchased a Lennox XC17 air conditioning unit (and heating unit also). Anyway, the air conditioning doesn't even cool my upstairs as well as my old unit. The unit is twice the size, and they made some mighty big guarantees on satisfaction. They came once and adjusted the guages and spoke of 100's of different setting changes to make this right. Whatever he did was meaningless and changed nothing. Next they came and added a return air vent in the basement out in the hallway from the unit. This really made no impact either. There could be a slight change but nothing notable. I paid 12,000+ for this unit. I've made it clear that I am not really interested in energy saving...my energy bills are quite nice. I wanted a unit like they described...that would cool evenly and continually, and circulate the air continually. Shouldn't it be cooling my upstairs as well?? What could be the problem?

If they did not modify or change the duct work and essentially just replaced unit for unit then you should notice little change between the systems. Keep in mind that we are seeing extreme heat all across the country, including KY. If the duct work was changed then they messed something up.

Re: How do you check an ac unit?

Scott,

Thanks for responding. Is changing the duct work something they should have already considered. For $12,000, I do expect it to cool my upstairs. Duh! I hope they get that. I do understand that the upstairs air will always feel a bit less cool than downstairs, but we are talking a major difference. You can feel the uneven heat feeling all over up there. You can also feel the air coming from the vents....it's just not circulating and keeping the upstairs cool. The downstairs has been very cool during this heat. So could the extreme heat still be the only reason for it not cooling upstairs?

One technician said quote..."these energy saving units aren't designed to do what the old ones did". I told him that my old one cooled the upstairs better than this one, and I could not settle for this. He made me feel like things were not going to get better. Why would he attempt to downplay the satisfaction this equipment could achieve....when I sit with a guarantee of 100% satisfaction for 3 yrs and a 5 year free maintenance plan.

Re: How do you check an ac unit?

Vivian, You said that the unit was twice as big. Do you mean in size or tonnage? If they increased the unit in tonnage that much it could be possible that it is too big. The unit will short cycle and not run long enough to properly dehumidify etc.

Re: How do you check an ac unit?

Originally Posted by DavidR

Sadly enough Darrell probably 90% of HVAC contractors don't have a clue on how to measured delivered BTUs..

There is the standard formula, plus the equipment manufactures provide a air flow chart to determine CFM vs Static Pressure and CFM vs Temperature rise. . But that will never show "delivered" BTU's This topic is hotly debated even on HVAC sites. So this type of testing is outside of the range of home inspection.

But since a new HVAC system can cost a lot of money people expect some level of inspection. Running the system is a KISS method of checking the system. But don't stop there. That is why most list the date of manufacture. ( is it still under warranty) Checking the filters to see if they have ever been changed. Is the outdoor unit half plugged up with dog hair and grass clippings. I think the IR gun is a very useful tool. At least your have a picture of what you saw, vs saying is was cool or warm. Also check the condensate drain, is it dripping like it should? Take a few pic's of the ducts, noting the R level. If they (buyers) want a more detailed inspection, this is were you find somebody that specializes in this type of work and has the equipment to measure it. As someone posted before just taking your hand and feeling the refrigerant pipes will tell you if the A/C unit is working. Won't be specific, but will clue you into the possible need for service. I also just hold my hand over the out door unit fan and expect to feel warm air. No warm air means somethings not right, took all of 2 seconds to check too.

FWIW, a friend just called and ask me to look at a house he just bought in another town. It passed all the inspections, but he told me the air does not seem to be flowing very strong as it's not getting cool now that its hot outside. (100+) I will head up there in the next few days with my inspection camera, and look at the A/C coil on the inside.
He did tell me the filter look like it had been there a year as it weight like 5 pounds. I will be curious as to what the report said. But suspect the A/C coil is in need of cleaning.

I'm sure its in the report, but do Home Owners really understand what was written?
Saying it needs service or cleaning, might be and understatement.

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